Technical Field
The present disclosure relates to a position indicator that is used with a position detecting device and is suitable as e.g. an electromagnetic induction system, and a position indicator cartridge.
Description of the Related Art
A coordinate input device of an electromagnetic induction system is composed of a position detecting device including a sensor made by disposing a large number of loop coils in the X-axis direction and the Y-axis direction of coordinate axes and a pen-shaped position indicator having a resonant circuit composed of a coil that is wound around a magnetic core and is as an example of an inductor and a capacitor.
Furthermore, the position detecting device supplies a transmission signal with a predetermined frequency to the loop coil of the sensor and transmits the transmission signal to the position indicator as electromagnetic energy. The resonant circuit of the position indicator is configured to have a resonant frequency according to the frequency of the transmission signal and stores the electromagnetic energy based on an electromagnetic induction effect between the resonant circuit and the loop coil of the sensor. Then, the position indicator returns the electromagnetic energy stored in the resonant circuit to the loop coil of the sensor of the position detecting device.
The loop coil of the sensor detects the electromagnetic energy from this position indicator. The position detecting device detects the coordinate values of the X-axis direction and the Y-axis direction over the sensor, indicated by the position indicator, on the basis of the position of the loop coil that supplied the transmission signal and the position of the loop coil that detected the electromagnetic energy from the resonant circuit of the position indicator.
In FIG. 8, one example of a schematic configuration of a conventional pen-shaped position indicator 100 is shown. The position indicator 100 of the example of FIG. 8 is a position indicator described in Patent Document 1 (Japanese Patent Laid-Open No. 2009-86925).
A case (chassis) 101 of the position indicator 100 has a bottomed circular cylindrical shape formed of a first case 102 and a second case 103 that are assembled and joined in an axis center or axial direction. On one end side of the first case in the axial direction, an opening 102a for externally protruding the side of one end 109a of a bar-shaped core body 109 in which the side of the one end 109a serves as the pen tip is formed. In the hollow part of the case 101, a coil 104, a writing pressure detector 105, and a printed board 107 on which electronic components such as a capacitor 106 that forms a resonant circuit with the coil 104 are mounted are sequentially lined up in the axial direction and are housed.
The coil 104 is wound around a ferrite core 108 as an example of a circular cylindrical magnetic core having a through-hole 108a along the axial direction. The core body 109 is formed as a component that is not mechanistically joined to the ferrite core 108 and is provided to penetrate through the through-hole 108a of this ferrite core 108. Furthermore, the writing pressure detector 105 is housed on the side of the ferrite core 108 opposite to the opening 102a of the first case 102 and the other end 109b of the core body 109 is fitted to the writing pressure detector 105. The core body 109 is moved and displaced in the axial direction according to the applied writing pressure. The writing pressure detector 105 detects the movement and displacement caused in the core body 109 as the writing pressure. The writing pressure detector 105 in this example is configured to detect the writing pressure as change in capacitance.
The writing pressure detector 105 is electrically connected to electronic components such as a capacitor on the printed board 107 by a terminal 105a and a terminal 105b and is electrically connected to one end and the other end of the coil 104. The writing pressure detector 105 forms a resonant circuit by the coil and a predetermined capacitor even when pressure is not being applied to the core body 109. When pressure (writing pressure) is applied to the core body 109, the capacitor capacitance changes in the writing pressure detector 105 and the resonant frequency changes. The position indicator 100 gives and receives electromagnetic waves to and from a position detecting device by this resonant circuit. The position detecting device detects a position indicated by the core body 109 of the position indicator 100 as the coordinate position at which the position detecting device is giving and receiving electromagnetic waves to and from the position indicator 100.
As described above, in the conventional position indicator of the electromagnetic induction system, by disposing the core body 109 through the through-hole 108a along the axial direction in the ferrite core 108, the configuration is made in which the pressure applied to the core body 109 is transmitted to the writing pressure detector 105 and the contact of the position indicator 100 to the input surface of the position detecting device can be detected.
Incidentally, due to preference for size reduction in recent years, demands for size reduction have been becoming stronger also in portable electronic equipment. Furthermore, the pen-shaped position indicator has come to be used with a position detecting device for this kind of small electronic equipment and a position indicator having a thinner shape is required.
However, in the case of the conventional position indicator of the above-described Patent Document 1, thickness reduction is difficult due to the configuration in which the bar-shaped core body 109 is inserted in the through-hole 108a along the axial direction in the ferrite core 108. Specifically, even in the case of this position indicator with the configuration of Patent Document 1, thickness reduction is possible if a high-accuracy through-hole in which the core body can be inserted can be formed in a thin ferrite. However, the ferrite is hard and it is difficult to form the through-hole with precise dimensional accuracy. In addition, there is a problem that the wall thickness of the ferrite core 108 becomes thin due to the formation of the through-hole and the ferrite becomes susceptible to breakages. Therefore, in the position indicator with the structure of Patent Document 1, thickness reduction is difficult substantially.
To solve this problem, a position indicator in which a protruding member serving as the pen tip is allowed to be provided without making a through-hole in a ferrite core is described in Patent Document 2 (Japanese Patent Laid-Open No. 2014-21674) for example.
FIG. 9A is a diagram depicting a configuration example of a position indicator 200 described in the Patent Document 2. Furthermore, FIG. 9B and FIG. 9C are diagrams for explaining the pen tip part of the position indicator 200 of this example.
As depicted in FIG. 9A, a case (chassis) 201 of the position indicator 200 of this example is composed of a resin or the like for example and is elongated in the axial direction. The case 201 internally has a hollow part whose cross-section is a circular shape, and is formed into a bottomed circular cylindrical shape whose one side is closed.
Furthermore, in the present embodiment, in the hollow part of the case 201, a ferrite core 203 as one example of a magnetic core around which a coil 202 as an example of an inductor is wound, a pressure sensing component (writing pressure detection component) 204, and a printed board 205 are held by a holder 206 composed of a resin for example and are housed.
One end side of the case 201 in the axial direction is deemed as the pen tip side of the position indicator 200 with a pen shape. On this pen tip side, the case 201 has an opening 201a formed of a through-hole for allowing a protruding member (pen tip member) 207 of a core body to protrude to the outside. In this case, the hollow part of the case 201 has a diameter larger than a diameter of the through-hole of the opening 201a, and a step part 201b is formed at the part of the opening 201a in the inner wall surface forming the hollow part.
A pedestal member 208 is disposed on a side of the opening 201a in the hollow part of the case 201. The pedestal member 208 has a thin circular column shape with such a diameter that the pedestal member 208 engages with the step part 201b and does not pass through the opening 201a (see FIGS. 9B and 9C). The ferrite core 203 has a thin circular column shape and is joined to the protruding member 207 to form the core body. Furthermore, the pedestal member 208 is bonded to one end surface of the ferrite core 203 by an adhesive and is fixedly provided. Moreover, the protruding member 207 is fitted to the pedestal member 208 and the ferrite core 203 insertably and removably through the opening 201a, which is a through-hole.
As depicted in FIGS. 9B and 9C, the protruding member 207 is obtained by monolithically forming a pen-tip main body part 2071 and a fitting protrusion 2072 by a single material. As depicted in FIGS. 9B and 9C, the pen-tip main body part 2071 is composed of a base part 2071a having a circular column shape with a diameter slightly smaller than the diameter of the opening 201a and a tip part 2071b having a spindle shape whose diameter gradually becomes smaller from the circular columnar base part 2071a toward the tip.
As depicted in FIGS. 9B and 9C, the fitting protrusion 2072 is formed at the central part of an end surface 2073 of the base part 2071a of the pen-tip main body part 2071 on the side opposite to the side of the tip part 2071b. As depicted in FIGS. 9B and 9C, the fitting protrusion 2072 has a quadrangular column shape as a whole and has a shape in which each of four corner parts formed by four side surfaces of the quadrangular column is cut into a rectangular shape in the direction toward the central axis.
Furthermore, the fitting protrusion 2072 is formed to gradually become thinner toward its tip side as depicted in FIGS. 9B and 9C. Moreover, the length of this fitting protrusion 2072 in the axial direction is selected to be larger than the thickness of the pedestal member 208.
The pedestal member 208 is composed of a material having a higher hardness than the protruding member 207 composed of a polyoxymethylene (POM) resin or an acrylonitrile butadiene styrene (ABS) resin, specifically, e.g., polycarbonate. Furthermore, the diameter of a through-hole 208a of the pedestal member 208 is set to a diameter that allows press-in fitting of the fitting protrusion 2072 of the protruding member 207.
Therefore, when the fitting protrusion 2072 of the protruding member 207 is inserted in the through-hole 208a of the pedestal member 208 as depicted in FIG. 9C, the fitting protrusion 2072 of the protruding member 207, whose hardness is lower than the pedestal member 208, is partly deformed. This causes the protruding member 207 to be fitted to the pedestal member 208 as depicted in FIG. 9C and become in a state of being held by the pedestal member 208 by being pressed-in, e.g., press-fitted. Thereby, the protruding member 207 is firmly fixed to the pedestal member 208.
Furthermore, on the side opposite to the opening 201a, the holder 206 includes a component disposing part 206b formed continuously with a locking part 206a and further includes a printed board placement part 206c formed continuously with the component disposing part 206b. Furthermore, the pressure sensing component 204 is held by the component disposing part 206b. Moreover, the printed board 205 is held by the printed board placement part 206c of the holder 206.
The pressure sensing component 204 is formed by sequentially lining up a ferrite chip 2041, a coil spring 2042, and an elastic body, specifically silicone rubber 2043 in this example, in the axial direction. Furthermore, in the component disposing part 206b, the pressure sensing component 204 is held in the state in which, by the coil spring 2042, one end surface of the ferrite chip 2041 forms a predetermined air gap Ar with the silicone rubber 2043 mounted on the end surface of a flange part 203a of the ferrite core 203.
Furthermore, when a pressing force (writing pressure) is applied to the protruding member 207 forming the pen tip by a user of the position indicator 200, the ferrite core 203 is biased and comes closer to the side of the ferrite chip 2041 against the biasing force of the coil spring 2042 according to the pressing force. Along with this, the inductance of the coil 202 changes in response to this, and the phase of radio waves transmitted from the coil 202 of the resonant circuit (resonant frequency) changes.